> For the complete documentation index, see [llms.txt](https://docs.justransform.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.justransform.com/development/mapper-and-map-chains/mapper.md).
# Mapper
Accessed through clicking Development > "**Mapper"** link on the left side panel of the application.
Mapping is the process of defining how data from one system or application should be transformed and mapped to another system or application. This involves specifying the relationship between fields in the source and target systems or applications.
On the top of the Mapper panel there are controls for:
* Creating a new Mapper process
* Opening a Mapper process
* Saving a Mapper process
Along with Editor controls:
* Undo/Redo
* Applying a new source model from file
* Applying a new target model from file
* Test Map
* Edit Map variables from the Groovy Script
* Edit Map Lookup Tables from the Groovy Script
* Edit functions
* Edit classes
* Edit scripts
* Excel Import/Export
* JTMapper Preferences
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